"or it would come to Farnborough to pick them up."
Nothing too much for a valued customer! IIRC personnel from either side were in and out of each others offices, hangars and aircraft all the time.
As Mechta says the great benefit of a Dakota was that you could cut holes in all over the place very quickly - and you could put a big, ungainly, prototype bit of kit or even an R&D proof of concept into them (normally Whisky Charlie) and see how they worked. If it was encouraging then you could spend money on miniturisation and detailed design.
FSL were able to get me a visit to the Nimrod R1 prototype at Boscombe AND a Q&A on state of the art of long distance navigation without bothering "higher authority". They did insist I signed the OSA tho - and bring along some ID.